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Samir Kharusi | all galleries >> Galleries >> Focal Lengths and Deep Sky Astrophotography > Canon 600mm+1.4x on Full 35mm Format
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17 Nov 2004 Samir Kharusi

Canon 600mm+1.4x on Full 35mm Format

Yiti, Oman

With the tele-extender we end up at 840mm focal length at f5.6. Unfortunately most DSLRs, even when modded, are rather insensitive to Blue. Consequently be prepared to shoot quite loooong integration times when you are chasing blue reflection nebulae like the above. Also, by current (2008) standards, the original Canon 1Ds used here was very noisy. Its predecessor, the Canon D30 (not the recent 30D!), was far too noisy for DSO imaging. Under the same conditions any of the current Canon DSLRs will yield a result with visibly less noise than the above example. This image was taken in the infancy/toddler days of DSLR astrophotography. At the time we did not really understand how, eg the colour response behaved, why H-alpha nebulae were so easily imaged by film but not by DSLRs, etc. Consequently my framing here was to check what colour that reddish star towards the top of the frame will come out. Aah, we have come a long way in a few short years :-) The image was shot at a site with quite heavy light pollution. I shot 5-minute subs because that sounded "long enough" but then I needed autoguiding. Luckily I had mains power available. Away from mains power autoguiding becomes a major pain. Most guiding CCDs and laptops are power hogs. For pleasant imaging in the boonies it is far more pleasant to avoid both autoguiding and laptops! More recent DSLRs also need shorter focal lengths to yield similar Fields-of-View. Their tiny pixels facilitate tight cropping. Consequently one can then use a shorter focal length, at a faster focal ratio (=shorter subs) and get away with no autoguiding; and still deliver a better end result :-)

Canon EOS 1Ds ,Canon EF600mm/4.0L + 1.4xII
31x5-minutes wide open at f5.6 and ISO 1250 full exif

other sizes: small medium large original auto
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Guest 23-Sep-2009 12:25
How did you do the tracking for the the 5-minute exposures ?
were you using the telescope mount ?
Guest 19-Nov-2008 00:04
Great Shot!